1. Field of the Invention
The present invention relates to a method and apparatus for handling network calls, and in particular to an interaction between a basic network and an intelligent network for handling network calls that require the support of the intelligent network.
2. Description of the Related Art
As the markets for public telecommunications services open up, call number portability is also required for IN service call numbers in many countries, that is to say IN service subscribers can keep their IN service call number when they change to another network operator/service provider.
An AT&T method for providing call number portability is known from the document EP-A-0 827 319. According to this method, when a call is made using a ported subscriber call number from a switching center, a query to a service platform (SCP) of an intelligent network for supporting handling of the call is started. The service platform (SCP) responds to the query by reporting to the switching center the “Location Routing Number”, on the basis of which the switching center routes the call to what is now the end switching center of the ported subscriber.
When a number of intelligent networks are present, operators of a public network must be able to route calls to individual IN service call numbers to that (intelligent) network which is supporting this IN service call number. Previously known solutions can lead to capacity problems in the IN service platforms (service control point SCP) or in the switching centers in the basic network (an intelligent network (IN) may be regarded as a basic network to which the IN functions comprising the service switching function SSF, service control function SCF, service management function SMF and the corresponding interfaces to the basic network have been added. Thus, in contrast to a basic call, an IN call requires not only the basic network functionality, but also the specific IN functions).
Normal IN services are those in which the public number dialed to set up a connection itself uniquely identifies the IN service subscriber. This is generally the case with dialed IN services. Possible special forms of dialed IN services, in which the IN service subscriber call number is checked only after accessing the IN service, using a dialog via the user channel, can in principle still be handled in the same way as normal IN services once the IN service subscriber call number has been received.
Previous solutions for IN service call number portability can be split into two categories:
A. Solutions with reactions on one's own IN service platform
B. Solutions with a query to a call number portability server before a query to one's own IN service platform.
A) Solutions with Reactions on one's own IN Service Platform
In these solutions, a normal IN query to one's own IN service platform is carried out by the basic network for all IN service call numbers (those which are supported by one's own IN service platform and those which are supported by service platforms in other networks). The IN service platform confirms whether it is supporting the dialed IN service call number or whether the dialed IN service call number is being supported by another network. In both cases, the IN service platform indicates to the requesting basic network switching center via the existing IN signaling how the call is to be handled further. For example, the IN service platform can instruct the switching center to pass on the call to the responsible network, by determining a network identification and reporting this to the switching center as routing information.
In Type A solutions, the capacity of the IN service platform is partially consumed for handling external IN service call numbers, which can lead to capacity bottlenecks for handling its own IN service call numbers. Since the basic network uses the same trigger mechanism for its own and for external IN service call numbers, load limitation procedures must not be used for queries from the IN service platform in the switching centers (call gapping functions) which would also affect external IN service call numbers (for example a service-related load limit).
B) Solutions with a Query to a Call Number Portability Server Before a Query to one's own IN Service Platform
In order to ensure that one's own IN service platform need handle only its own IN service call numbers, the basic network uses the IN signaling to ask for a special call number portability server (NP server; NP=Number Portability) for all the dialed IN service call numbers. The NP server confirms whether the dialed IN service call number is being supported in its own network or in another network. The NP server uses the IN signaling to instruct the requesting switching center how the call is to be handled further. For its own IN service call numbers, the basic network carries out a normal IN query to its own IN service platform following a query from the NP server. For external IN service call numbers, the call is routed to the responsible external network in accordance with the instructions from the NP server. In Type B solutions, the capacity of one's own IN service platform is protected, but additional basic network capacity is required for this purpose for prior queries in the case of a special NP server. If decoupled trigger mechanisms are used for the prior query in the case of the NP server and for the subsequent query in the case of one's own IN service platform, service-related and call-number-related load limitation procedures can be used without any restriction for the IN service platform (call gapping functions) in the switching centers.